This invention pertains to a machine for fabricating triaxial fabric, and more particularly to improvements in such a machine for the feeding under controlled tension of individual yarn ends and the guiding of yarn from the feeding means to the weaving mechanism under controlled tension and with minimum mechanical handling.
Triaxial fabric forming machines are disclosed, for example, in U.S. Pat. Nos. 4,015,637--Halton et al and 4,031,922--Trost et al, both of which are now of common assignment with the present application and both of which are incorporated herein by reference. Those patents both disclose vertically oriented machines with a rotating creel on a vertical axis carrying multi-end beams of warp supply yarn.
The multiplicity of yarn ends from these beams is guided inwardly and down to form two planar arrays aligned at the point of weaving along the fell line of the woven fabric. An individual yarn end, in successive stages of the triaxial weaving sequence, traverses from one end of an array to the other and then is transferred to the other array where it does the same thing. In such machines, the mechanism for maintaining uniform tension of each of the yarn ends is necessarily complex, in part because of the variation in individual yarn path lengths as the creel rotates, and in part because multiple ends are fed from each beam.
Various types of tension means, such as that identified by reference numeral 104 in FIG. 5 of U.S. Pat. No. 4,015,637, have been used. A specific mechanism for guiding the warp yarn ends as they traverse the weaving array is seen, for example, as track 40 in FIG. 2 of U.S. Pat. No. 4,036,262 along which travels yarn guiding divider plates 41 (as seen in FIG. 11). Divider plates (or guides 41) and track 40 together deflect the yarn path of each yarn end to provide an essentially constant length yarn path for that yarn end as it traverses about the array.
Still another form of warp yarn path compensator and guide is the closed path tubular guide 173, seen in FIG. 12 of U.S. Pat. No. 4,036,262.
Still other warp length compensating means for a triaxial weaving machine are disclosed in U.S. Pat. No. 4,170,249.
Notwithstanding these prior efforts to devise tensioning means and yarn path length compensators in a triaxial weaving machine, there remains a need for still further improvements with respect to these aspects in triaxial weaving machines. This need has become more apparent in the course of the recent development of methods and means for forming triaxial fabrics of high modulus fibers, such as graphite fibers. In conventional weaving with such fibers, efforts have been made to control the tension of individual yarn ends by virtue of the rolling friction of a yarn package on a supply spindle. No such tension controlling mechanism has heretofore been adapted in a triaxial weaving machine.
Moreover, informing fabrics from high modulus fibers, such as graphite, (beams) are undesirable because of the tendency of such high modulus fibers to break filaments or otherwise lose strength as they are wound onto a multi-end package.
It is also known that in certain circular knitting machines, rotating creels are provided with individual yarn packages mounted thereon. In knitting, however, unlike weaving, little or no yarn tension is desirable and for the most part yarn is fed from the individual packages on such creels with a minimum of tension.
There remains a need, therefore, for improved tensioning and yarn path length compensation means for triaxial fabric forming machines, and particularly for vertically oriented triaxial fabric forming machines with rotating creels.
More particularly, there remains a need for such improvements for use in the weaving of high modulus fibers.
It is, therefore, the general object of the present invention to provide such improved tensioning means, and to provide such means which more effectively control the tension in individual yarn ends of a triaxial fabric forming machine notwithstanding path length changes of an individual yarn end, and which permits the use of single end yarn packages.